Pressure vessel construction



y 1945- E. F. MILLER 2,375,999

PRES SURE VESSEL CONSTRUCTION Filed July 29, 1942 WlTNESSESi H INVENTOR M w E'Rmss'r F." MILLER.

474 444 BY I ATTORNEY Patented May 15, 1945 PRESSURE VESSEL CONSTRUCTION Ernest F. Miller, Lansdowne, Pa.,:assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 29, 1942, Serial No. 452,748

2 Claims.

This invention relates to pressure chambers, more particularly to those where bending stresses in the wall must be kept to a minimum, and has for an object to provide ideal shapes for such pressure vessel walls.

In certain types of pressure chambers, for example, marine condenser waterboxes, where economy of weight dictates the use of thin walls, there is presented a problem of keeping bending stresses in such walls to a minimum. The ideal shape of such a chamber would be that assumed by a soap film if the film were attached to the contour of the flange and air introduced beneath the film. Since the film would be in pure tension, this shape would be ideal. It would not, however, follow any pure geometric shape unless the flanges were parallel and of infinite length, in which event the film would be cylindrical, if the flange were circular, the film would assume a spherical shape.

A close approximation of the ideal may be obtained by developing the wall shape with circular arcs which would intersect the flange line. The maximum stress may be easily calculated and can be shown not to exceed those in a cylinder of the same radius. Because of the double curvature near the ends of a chamber, such as illustrated in the drawing, the stresses will be less than maximum and the effect of bending stresses because of departure from the ideal soap film would be secondary and negligible since the combined stress due to tension and bending must be less than the maximum.

Therefore, another object of the invention is to provide a pressure chamber whose wall, in all planes normal to a selected axis, presents circular arcs of either the same or of different radii.

These and other objects are efiected .by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is an end elevational view of a marine condenser, showing the waterbox thereof constructed in accordance with the present invention;

Fig. 2 is sectional view taken along the line IIII of Fig. 1 looking in the direction of the arrows, the figure being inverted for the sake of clearness; and,

Fig. 3 is a development diagram for producing from Fig. 1 the shape shown in Fig. 2.

Referring now to the drawing more in detail, there is shown, at In, a marine-type condenser which is of irregular cross section in order to best utilize the limited space available for mav rine installations of this character, the condenser comprising a shell ll having an exhaust steam inlet l2 and a condensate outlet l3. A plurality of tubes l4 extend longitudinally of the shell and have their terminal portions extending through and carried by end tube plates l5. The periphery of the tube plate l5 (Fig, 2) extends beyond the shell H to provide a flange I! to which is attached the flange. l8 of a waterbox l9 having a wall structure 20, whose design constitutes the subject matter of the present invention.

The present invention is based on the thought that the optimum cross section for any pressure vessel is circular, as with such shape the walls are in pure tension, there being no bending moments present. Therefore, it is proposed that all sections of the wall 20 of the waterbox structure 19, for example, those lying along the lines a, b, c, d, e, j, g, and h of Figs. 1 and 2, shalltbe circular arcs, either of the same or of varying radii, with the arcs tangent to or intersecting the flange I8 at opposite sides thereof. With such a construction the point of maximum height for any section will lie midway of the opposite flanges. In the construction illustrated, such points of maximum height would lie along the dot-dash line IIII of Fig. 1.

Using the same radius for all of the circular arcs, the latter can be laid off, as in Fig. 3, to determine the maximum height of each are above the flange l8, such height being transferred or laid ofif on the line a, b, 0, etc., of Fig. 2, thereby determining the outline or shape of the wall 20. While in the construction herein illustrated, circular arcs of the same radii have been used, it will be apparent that these radii may vary in length for difierent planes, for example, a radii of maximum length might be used at the section b with the radii of adjacent planes decreasing in length from the line b toward each end of the flanged structure.

Furthermore, while the lines a, b, c, d, e, etc., have been shown as parallel to each other and normal to the straight portion of the flange l8, these lines may be normal to any selected straight or curved line; for example, they might be normal to the dot-dash line IIII of Fig. 1.

Referring to Fig. 3, the circular arcs lying along the lines a, b, 0, etc., are indicated by the reference characters a, b, c, etc., each are having the same radius indicated by the arrow and having the centers of radius indicated at a", b", 0'', etc,

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall .be placed thereupon as are specifically set forth in the appended claims.

What is claimed is: 1. In a surface condenser waterbox, a head axis of said opening, each of said arcs intersecting the flange at opposite sides of the opening.

2. In a surface condenser waterbox, a head comprising a domed wall structure and a flange about the edge of said wall, the opening defined by said flange being elongated and provided with rounded corners, and the domed wall structure being generated by the travel of a circular are from one end of the elongated opening defined by the flange to the other end thereof with the arc tangent to the sides of said elongated opening throughout its travel.

ERNEST F. MILLER. 

